The optical imaging quality of large telescope mirrors is substantially affected because they tend to deform under their own weight. In configuring an edge supporting system, one therefore strives to minimize deformations of the mirror in the direction of its axis by selecting a suitable distribution of supporting forces. Such deformations have an intense effect on the imaging quality of the mirror. The influence of different supporting force distributions on the deformation of a large telescope mirror are described, for example, in "Applied Optics, Volume 7, Number 6", pages 1207 to 1212, June 1968.
In edge supporting systems which have been realized to date, the supporting forces are always radial forces, that is, forces which are directed toward the center point of the mirror whereby the totality of the supporting forces are viewed as being especially advantageous as a cosine-like distribution in the form of thrust or push forces on the lower half of the mirror and tension or pull forces on the upper half thereof. As a practical matter, the supporting forces are, as a rule, applied through a system of counterweights arranged uniformly on the periphery of the mirror. These forces act on the peripheral edge of the mirror via levers as explained, for example, in No. DE-OS 24 14 266. In this connection, the cosine supporting force distribution results from the arrangement of the pivot axes of the levers tangential to the edge of the mirror.
In addition, No. DE-OS 29 03 804 teaches that a tangential supporting force distribution with a sine-like envelope of the magnitudes of forces can be superimposed upon the radially directed supporting force distribution with a cosine-like envelope. This leads to the condition that the resultants of the forces acting on the edge of the mirror all act in the direction of the projection of the gravity force in the mirror plane and have the same magnitude. In this known edge supporting system, the supporting forces are applied in an embodiment which is especially suitable for parallactic assembly by means of counterweights on levers which are pivotable simultaneously about two orthogonal axes. The realization of such a lever system requires a relatively high expenditure.